Neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is an example of neurostimulation in which electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control. Other examples include deep brain stimulation, cortical stimulation, cochlear nerve stimulation, peripheral nerve stimulation, vagal nerve stimulation, sacral nerve stimulation, etc. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nerve tissue. Specifically, applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain.
Neurostimulation systems generally include a pulse generator and one or more leads. The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generation circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator. Specifically, feedthrough wires typically exit the metallic housing and enter into a header structure of a moldable material. Within the header structure, the feedthrough wires are electrically coupled to annular electrical connectors. The header structure holds the annular connectors in a fixed arrangement that corresponds to the arrangement of terminals on a stimulation lead. The terminals of a stimulation lead are electrically coupled to conductors disposed within the insulative body of the stimulation lead. Electrodes are also electrically coupled to the conductors on a distal end of the stimulation lead. Electrical pulses are conducted from the pulse generating circuitry through the feedthrough wires, the annular connectors, the terminals, and the conductors to the electrodes to stimulate tissue of the patient.
The charge transfer characteristics of electrodes are important in avoiding degradation of the conductive material of the electrodes and in avoiding injury to tissue of the patient. Specifically, when implanted within a patient, the electrodes of a stimulation lead are essentially immersed in aqueous solution. Application of electrical current through the conductive material in such an environment may compromise their chemical stability by promoting corrosion and degradation. Corrosion of the stimulation electrode may lead to premature failure of the stimulation lead and adverse tissue reactions triggered by the release of corrosion products. In addition, an adverse tissue response may be trigged by irreversible faradaic reactions (such as electrolysis of water). In general, neurostimulation systems limit the current density of stimulation pulses to avoid these issues.
In one embodiment, a method, of fabricating a stimulation lead for stimulating tissue of a patient, comprises: providing a lead body, the lead body comprising a plurality of conductors embedded within insulative material; providing a plurality of terminals; electrically coupling the plurality of terminals with the plurality of conductors; providing a plurality of electrodes, the plurality of electrodes comprising a plurality of substantially continuous longitudinal trenches on a surface of the electrodes, the electrodes comprising areas of reflow material forming microstructures substantially continuously along walls of the longitudinal trenches; and electrically coupling the plurality of electrodes with the plurality of conductors.
The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims.